The Ghrelin Made Me Eat It

Call it the chemistry of overeating. This hunger hormone may be behind that obsession you have with brownies.

Why, even when we are no longer hungry, is one bowl of ice cream sometimes not enough? Researchers at UT Southwestern have found that the hormone ghrelin plays a role in making people who are full continue to feel the need to eat. Mice given ghrelin became obsessed with their food.

Ghrelin is a hormone produced by the body when hungry.

When the mice were then given ghrelin, they strongly preferred being in the room that had contained the tasty food, even though the room was now empty and the mice were full.

Laboratory mice are normally fed rodent chow. Like humans, they prefer tastier food. Two experiments conducted by the researchers showed how ghrelin kept their mind on this preference and intensified it. In the first experiment, mice had to poke their nose into a hole and wait to receive a pellet of high-fat food. Normal mice gave up when the food didn't appear after a short period. Mice given ghrelin were much more persistent and continued to wait for a much longer time until the food magically appeared.

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In the second experiment, the researchers looked at the behavior of mice that were fully sated. These mice had been previously fed high-fat food in one room, while a second room had contained only their regular bland mouse chow. When the mice were then given ghrelin, they strongly preferred being in the room that had contained the tasty food, even though the room was now empty and the mice were full. Apparently, the memory lingered. Mice not given ghrelin didn't care which room they were in.

Blocking the action of ghrelin prevented mice from spending as much time in the pleasant room that had once contained the tasty food.

These experiments raise the possibility that some day, it may be possible to stop people from overeating by lowering how much ghrelin they produce or by blocking its effects. Just knowing that eating a second helping of ice cream is overdoing it often isn't enough. Being less focused on food so a person no longer wants that second bowl of ice cream should work much better. Ghrelin metabolism offers this promise.

The results of the study were first published online December 24, 2009 and will appear in a future issue of the journal Biological Psychiatry.